Weight of water

[MBMorgan]

I do have a scale, and concur with all comments above re using it.

My point is that published information re the weight of one cup of water, in grams, varies from 227 to 240 grams. Why, and what is accurate?

OK ... so 1 fluid ounce = 29.57ml. 1ml of water "officially" weighs 1 gram, so 1 fluid ounce of water "officially" weighs 29.57 grams. Therefore 1 cup (8 fluid ounces) of water "officially" weighs 236.56 grams. Round that off to 237 grams per cup of water because few kitchen scales can measure fractions of grams.

So, to answer your question: Apparently none of your measurement sources are accurate. They are all, however apparently close enough to get away with using them for baking. Frustrating, huh?

[MBMorgan]

RonB - Yeah ... I see multiple "standard" grams/ounce and ml/fluid ounce conversions out there, too. One of these days, I'll have to see if I can figure out which are correct. Meanwhile ... much like Kenji, KAF, and probably many others, I just can't bring myself to care enough to make the effort.

[MBMorgan]

RonB - After a bit of digging, here's what I've found:

VOLUME: 1 fluid ounce = 29.57353 mL (29.57 grams if water)

WEIGHT: 1 ounce (avoirdupois / US Customary Unit) = 28.34952 grams

Ref: https://www.govinfo.gov/content/pkg/...3e4.pdf#page13

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There is also the Troy ounce in the US ... used only for fine metals and coinage

WEIGHT: 1 ounce (troy) = 31.10348 grams
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No Idea where your "25.2" came from.

[RonB]

I just did a search using Bing and the above values showed up. I don't think it's worth repeating since neither of us will use 25.2 g.

[yakima]

Yikes.
What weight do you guys on this site use?

[rickgregory]

I don't. I weigh the liquid too. If a recipe doesn't say something like "1 cup (237g)" then I use another recipe. I've never seen a recipe that is so good it's the only one out there for a given dish.

[shify]

We don’t. Use a recipe written in grams (or ml) and not one in fluid ounces.

I bet if you fill your Sur La Table 1 cup measurement cup 10 times, you’ll wind up with 10 different weight

[MBMorgan]

1 cup water = 237g

BTW, unless your kitchen scale is a lab reference scale sitting on a stone table under a glass cover, you'll probably get a different value, too ...

[Donw]

MBMorgan is correct. One problem in measuring water in the home is the measurer forgets about reading the volume at the liquid meniscus. Our government’s National Institute of Standards and Technology has published a Metric Cooking guide which uses 240 grams per cup which is close enough to the real value of 237 grams for day to day cooking.

https://www.nist.gov/pml/owm/metric-cooking

[rickgregory]

temperature will make a minor difference too since hotter liquid will slightly expand.

[yakima]

So who is going to tell Kenji and King Arthur?

[MBMorgan]

So who is going to tell Kenji and King Arthur?

I'm pretty sure that they both know ... and that neither cares a lot. At 227g, they are only off by about 10g from the actual weight of a cup of water. 10g is roughly 1/3 oz. ... which is a difference that is barely enough for the average kitchen scale to even measure accurately. I wouldn't worry about it ... or them ... or the future of baking ...

EDIT: I'm just guessing here, but I'm thinking Kenji and KAF probably got their 227g figure by simply assuming that a cup of water weighs exactly 8 ounces (remember the saying: "a pint is a pound the world around"?) ... which just happens to be 227g.

[Gunbe]

You do know that one cup is not an absolute measure? Do you mean US customary or legal, metric, korean, canadian or the UK cup? They are all different volumes and therefore a cup of water will have different weights.

[Attjack]

I have 2 scales in my kitchen including 1 for stuff like water and flour and 1 that is for fine measurements like yeast and salt.

[hoovarmin]

Same

[yakima]

Good reminder Attjack. My reloading scale can do grams and grains, and has test weights.